Remote strike off



Nov. 27, 1956 J. M. BLEUENSTEIN 2,771,649

REMOTE STRIKE OFF Filed Aug. 12, 195s .VIII

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J M. BL 50E/v5 TE//v IN V EN TOR.

ArroRA/E ys 2,771,649 REMTE STltilE @EF Julius M. Bleuenstein, Detroit, Mich., assigner to Ford Motor Company, Dearborn, Mich, a corporation of Delaware Application August l2, i953, Serial No. 37.3,St 2 Claims. (Cl. Z22-i935) This invention relates to the founding art and more specifically to that portion of the foundi Cg art appertaining to the high volume production of relatively small castings. This invention also relates to, and is improvement upon, the well known shell mol In the production of larve numbers ci castings the use of stack molds is a well known procedure. In the preparation of stack molds two cornplementary mold halves are superimposed upon each other to produce a completed mold, each completed mold usually being provided with cavities to form a large number of individual pieces. These assembled mold pairs are then stacked vertically and clamped into position. While so stacked, the entire assemblage is poured simultaneously through suitable risers.

When the shell molding procedure was adapted to stack molding, a metal pattern was provided containing positive patterns of the part to be produced. This pattern was then struck oit level, with the depth or" the sand being kept at a minimum considering the thickness ot the castings. The molds were, of course, heat cured in this metal pattern box. Since the faces of the mold to be placed adjacent each other in assembling the complementary pairs were produced and cured against a finished pattern, no difculty was experienced in producing a metal-tight seal between the complementary mold halves. Leakage was no problem as long as only a single pair of mold halves was employed. When it was attempted to stack these completed molds, diiculty was encountered with leakage of metal between the adjacent molds due to the unevenness produced in the struck ed surface due to the differential shrinkage of the sand during curing. In an attempt to alleviate this diiculty, the art resorted to an operation necessitating the placing of the nished surface of a mold half upon a llat surface and a grinding operation on the opposite surface in an attempt to produce metal-tight assembly. However, due to the fact that stresses are set up in the sand mixture during curing, the grinding operation caused Warpage due to the release of these stresses and simply succeeded in transferring undesirable leakage and dash from the risers intermediate the individual molds to the castings themselves.

The instant invention has been developed to avoid this ditlculty and takes advantage of the fact that the amount of shrinkage of the sand mixture during curing is directly proportional to the thickness of the sand layers. This invention may best be explained by reference to the drawings in which:

Figure l is a planned view of a of mold halves.

Figure 2 is a cross section of Figure l along the line 2 2 showing the pattern filled with sand and struck ott but not cured, and

Figure 3 shows the cured mold in place in the metal pattern.

Referring to Figure l the pattern is denominated generally as 10. This pattern comprises a planar base 1li surrounded by side walls l2 secured to base ll upon which is secured the replicas i3 on the castings to be produced. lt will be noted that pattern it? is provided with a central gate i4 and four corner risers lo'. Attention is invited to the tact that each of the risers is provided with a substantial collar ot metal. ln the case pattern for production Patented Nov. 27, 1956 of central risers l5, 'this collar has been denominated 16.

ln operation the sand mixture is heaped upon pattern it? and struck oit as shown in Figure 2. T his is accomplished by strike ott bar 17. Particular attention is invited to the fact that strike ott bar l? does not Contact pattern ltr? but clears pattern itl by a substantial amount. This clearance is indicated by the letter C in Figures 2 3. it will be observed that wall l2 of pattern 10 is equal in height to the highest portion of each of the individual. casting clusters. ln the case of the casting clusters, this high point is advisedly that portion ot' the pattern surrounding the riser. A similar consideration applies to central riser ld.

When this mold is struck ott and cured, the structure depicted in Figure 3 is obtained. ln Figure 3 the shrinkage ot` the sand on curing has been exaggerated in the interest of clarity. This invention provides a minimum sand thickness over wall 12 and around each of the gates and risers. This minimum thickness of sand heats and cures more rapidly than the adjacent thicker layers and hence has a lesser amount of shrinkage. Thus, when a plurality of completed molds are produced by assembling the half molds formed in patterns lil in pairs and these assembled pairs are stacked, the actual contact by the adjacent pairs will be limited to the area which was directly over the walls l2 and which surrounded the risers id and gates l5. Such a stack may be produced with no pasting between adjacent molds or at best only a minimum of pasting and reliance placed upon the comparatively unshrunken collars of sand surrounding each metal passage to prevent the undesired lateral flow of metal during pouring. This structure also localizes upon the risers any metal leakage that does occur where it is relatively harmless.

I claim as my invention:

1. The process of producing a molding element comprising providing a metal pattern with a planar sand receiving base, replicas of the article to be produced on the base, a raised wall surrounding the base, and holes in the base to provide gates and risers, each of said holes being surrounded by a boss or mass of metal elevated from the base a distance approximately equal to the height of the wall, heaping the pattern with a heat settable mixture of sand and a resin, striking ott the pattern promptly and before excessive setting of the mixture has taken place, said strike ot operation being conducted so as to leave a thin layer of sand over the wall and bosses, and finally applying heat to cure the mixture in the pattern and cause dilerential shrinkage of the mixture.

2. The process for producing a stack mold for the reception of molten metal comprising providing a metal pattern with a planar sand receiving base, replicas of the articles to be produced on the base, a raised wall surrounding the base, and holes in the base to provide gates and risers, each of said holes being surrounded by a boss or mass of metal elevated from the plane of the base a distance approximately equal to the height of the wall, heaping the pattern with a heat settable mixture of sand and resin, striking oli the pattern promptly and before excessive setting of the mixture has taken place, said strike olf operation being conducted so as to leave a thin layer of sand over the wall and bosses, applying heat to cure the mixture in the pattern and cause differential shrinkage of the mixture, removing the molds so produced from the pattern and stacking a plurality of molds so produced to complete a stack mold.

Ensign et al. Oct. 13, 1953 OTHER REFERENCES American Foundryman, August 1952, pages 42-46. 

